If you’re happy with it still using the new tooling, the easiest approach is probably just to edit the project file (csproj). Right-click on the project in Solution Explorer and you should have a context menu option of “Edit <yourproject>.csproj”. Click on that, and just change
<TargetFramework>netcoreapp1.1</TargetFramework>
to
<TargetFramework>net46</TargetFramework>
… and I suspect you’ll be good to go. (It may confuse VS for a little while as it restores appropriate packages etc.)